Calculation method, image-capturing method, and image-capturing apparatus

Abstract

A calculation method, an image-capturing method, and an image-capturing apparatus are provided which can easily calculate a shear amount produced by an optical element arranged on an optical path of an interference optical system. A calculation method according to the present disclosure is a calculation method of calculating a shear amount produced by a predetermined optical element which is arranged on an optical path of an image-capturing optical system. The calculation method includes a step of capturing an interference contrast image of a quadric surface included in an object surface by the image-capturing optical system, a step of measuring a fringe interval of interference fringes included in the interference contrast image, and a step of calculating the shear amount based on a constant in a formula expressing the quadric surface and the fringe interval.

What is claimed is: 
     
         1 . An information processing apparatus configured to control an imaging apparatus including an interference optical system having a predetermined optical element arranged on an optical path, the information processing apparatus comprising:
 a processor configured to:   acquire, from the imaging apparatus, an interference contrast image of a quadric surface included in an object surface by the interference optical system;   measure a fringe interval of interference fringes included in the interference contrast image; and   calculate a shear amount based on a constant in a formula expressing the quadric surface and the fringe interval, wherein   the shear amount is a lateral shift between the two parallel light beams of illumination light transmitted through the predetermined optical element,   the quadric surface is at least one of a surface of a spherical body, a surface of a circular column, or a parabolic surface,   the formula expressing the surface of the spherical body is x 2 +y 2 +z 2 =R 2 , the formula expressing the surface of the circular column is s 2 +z 2 =R 2 , the formula expressing the parabolic surface is z=as 2 , z denotes a position in the height direction, x and y denote horizontal positions, s denotes a position in the shear direction, and R and a denote constants, and   the shear amount is calculated based on the interference fringes obtained by illuminating the quadric surface with ordinary light and extraordinary light that are transmitted through the predetermined optical element, and the calculated shear amount is used for controlling or managing the imaging apparatus or the predetermined optical element.   
     
     
         2 . The calculation method according to  claim 1 , wherein
 the interference optical system is a confocal optical system, and   the calculation method further comprises:   a step of measuring a three-dimensional shape of the quadric surface by using the confocal optical system; and   a step of estimating the constant based on the three-dimensional shape.   
     
     
         3 . The calculation method according to  claim 1 , wherein in the step of calculating, a change in a slope of the quadric surface in the shear direction is approximated by a linear function. 
     
     
         4 . An image-capturing method comprising:
 calculating step of calculating a shear amount produced by a predetermined optical element which is arranged on an optical path of an interference optical system;   a step of adjusting a position of the predetermined optical element, by moving at least in a direction crossing the optical axis of the interference optical system, based on the shear amount calculated in the step of the calculating such that a path difference between two rays of light divided by the interference optical system becomes a predetermined value; and   a step of capturing an interference contrast image of a sample by the interference optical system after the step of adjusting, wherein   the step of calculating comprises:
 a step of capturing an interference contrast image of a quadric surface included in an object surface by the interference optical system; 
 a step of measuring a fringe interval of interference fringes included in the interference contrast image; and 
 a step of calculating the shear amount based on a constant in a formula expressing the quadric surface and the fringe interval, 
   the shear amount is the lateral shift between the two parallel light beams of illumination light transmitted through the predetermined optical element,   the quadric surface is at least one of a surface of a spherical body, a surface of a circular column, or a parabolic surface, and   the formula expressing the surface of the spherical body is x 2 +y 2 +z 2 =R 2 , the formula expressing the surface of the circular column is s 2 +z 2 =R 2 , the formula expressing the parabolic surface is z=as 2 , z denotes a position in the height direction, x and y denote horizontal positions, s denotes a position in the shear direction, and R and a denote constants.   
     
     
         5 . The image-capturing method according to  claim 4 , wherein the sample is a transparent substrate or a transparent wafer. 
     
     
         6 . An image-capturing apparatus comprising:
 an interference optical system;   a predetermined optical element being arranged on an optical path of the interference optical system; and   a processing unit configured to execute:   a process of capturing an interference contrast image of a quadric surface included in an object surface by the interference optical system;   a process of calculating a shear amount of the predetermined optical element based on a fringe interval of interference fringes included in the interference contrast image and a constant in a formula expressing the quadric surface; and   a process of adjusting a position of the predetermined optical element, by moving at least in a direction crossing the optical axis of the interference optical system, based on the shear amount calculated in the calculating process such that a path difference between two rays of light divided by the interference optical system becomes a predetermined value,   wherein   the shear amount is the lateral shift between two parallel light beams of illumination light transmitted through the predetermined optical element,   the quadric surface is at least one of a surface of a spherical body, a surface of a circular column, or a parabolic surface,   the formula expressing the surface of the spherical body is x 2 +y 2 +z 2 =R 2 , the formula expressing the surface of the circular column is s 2 +z 2 =R 2 , the formula expressing the parabolic surface is z=as 2 , z denotes a position in the height direction, x and y denote horizontal positions, s denotes a position in the shear direction, and R and a denote constants, and   the shear amount is calculated based on the interference fringes obtained by illuminating the object having the quadric surface placed on a stage with ordinary light and extraordinary light that are the two parallel light beams.   
     
     
         7 . The image-capturing apparatus according to  claim 6 , wherein
 the interference optical system is a confocal optical system, and   the processing unit further executes a process of estimating the constant based on a three-dimensional shape of the quadric surface, the three-dimensional shape being measured by using the confocal optical system.